Put on a big pot of salted water for the pasta before you start with the pesto.
In a small pan over medium high heat, roast the walnut halfs until they are slightly browned.
In a small food precessor or in a bowl using a stick blender, combine the washed and drained spinach, the parmesan, the walnuts and the garlic.
Add a generous splash of olive oil and start mixing until it all comes together in a creamy pesto.
Keep adding olive oil until you have the desired texture.
Season with salt and pepper.
Cook the pasta according to package.
Mix the drained pasta with the pesto and serve with parmesan on the side.